I'm having issues with these parts on my 2000 S4. My car was running really poorly at idle, chugging, but running fine at any rpm over 2000. Yesterday, I replaced one module (what I thought to be the bad one) and it immediately corrected the idle problem, but created a mid-range and upper rpm shake/shudder while driving under 30% + load. I swapped the modules around and nothing corrected it.

I started it this morning and the same idle problem is back. I always have misfire issues with this car, I'm about to park it on train tracks.

Can anyone help me (with the misfire issue)? Is there a way to test the modules? One shows no resistance, the other shows some. I have dielectric grease on the connections. Coil packs are 2 yrs old. Denso iridium and stock plugs tested. No known boost leaks. New turbos. New head gaskets. New everything.

 

Probably should have been more specific...do you need to replace in pairs? If one is bad and you run the engine with a good one will it damage the good one? Will a bad coil pack damage them?